Pneumatic false twisting interlacer

ABSTRACT

Apparatus for interlacing a filament yarn to give it compactness and other characteristics of a twisted yarn comprising a pair of spaced oppositely functioning pneumatic false twisters with the downstream twister having a smaller yarn passage than the upstream twister.

1 1 Umted States Patent 1191 1 1 5, Lloyd et a]. Dec. 4, 1973 [54] PNEUMATIC FALSE TWISTING 3,115,691 [2/1963 Bunting, Jr. et a]. 28/1.4

INTERLACER 3,125,793 3/1964 Gonsalves 3,286,321 11/1966 Fletcher et a] 28/1.4 X [75] Inventors: Neil E. Lloyd; Walter B.

M th b th f R k Hill 511 FOREIGN PATENTS OR APPLICATIONS A g e Celanese Corporation, e York, 691,566 2/1970 Netherlands 57/34 B N.Y.

7 Primary ExaminerJ0hn Petrakes [22] Flled June 1970 Attorney-Thomas J. Morgan and Stephen D. Murphy [21] App]. N0.: 42,404

[57] ABSTRACT [52] US. Cl 57/773, 28/1.4, 28/7212, Apparatus for interlacing a filament yam to give it 5 7/34 57/157 F compactness and other characteristics of a twisted [51] Int. Cl. D02 1/08, DOlh 7/92 yam comprising a pair of Spaced oppositely function [58] Fleld of Search 57/773, 77.45, 34 B, mg pneumatic false twisters with the downstream 57/157 {128/141 72-12 twister having a smaller yam passage than the upstream twister. [56] References Cited 1 UNITED STATES PATENTS 19 Claims, 5 Drawing Figures 3,110,151 11/1963 Bunting, Jr. et a1. 28/1.4 X

PATENTEU 4 I973 mvmon NEIL E. LLOYD WALTER B. MATHER,]1I

ATTORNEY PNEUMATIC FALSE TWISTING INTERLACER BACKGROUND OF THE INVENTION The present invention relatesto a novel apparatus and process for interlacing the filaments of a .multifilamerit yarn so as to impart thereto the characteristics of a yarn which has twist.

In the production of continuous filament yarns they are usually collected either with a ring and traveller takeup or with a horizontal zero twist takeup. The ring and traveller imparts a small amount of twist, the exact magnitude depending upon the rotational speed of the collector and the running speed of the yarn. While either the low twist, e. g. about 0.25 turns per inch; or the zero twist yarns are suitable directly for certain end uses, for most knitting and weaving purposes the yarns are not suitable for use as is. The high speeds encountered in processing frequently make the filaments bal- I loon out and separate from the main bundle with subsequent breakage due to snagging upon the supply package from which it is withdrawn or from contact with yarn guiding surfaces over which it is drawn. To prevent this possibility, and for other reasons as well, it is customary to twist the yarn whereby the tendency of individual filaments tosplay out and/or break is minimized. Moreover, even if anindividual filament should break it will be held in its own bundle, rather than snarling the nearby yarns.

To put three or more turns per inch into a yarn is relatively time consuming, i.e. the maximum linear speed of the yarn will be only a few hundred meters per minute.. Accordingly, if such twisting were done on the yarn as first taken up after extrusion, it would limit the extrusion speed. Consequently, it is the practice to extrude and collect the yarn and then to transfer the yarn to another machine where it is twisted, this obviously entailing additional equipment and manual labor.

Techniques have therefore evolved to eliminate twisting, i.e. to perform its compacting function in some other manner at speeds high enough not to slow down extrusion. One such technique is to glue the filaments together lightly at spacedlocations as by applying yarn size. Another technique for folding filaments into the body of the yarn to maintain a compact bundle is described in U. S. Pat. No. 2,673,442 which described subjecting the yam to two sequential false twisting devices operating in opposite senses, the false twisting devices being skew guides, rotating twisters, helical groove guide members or fluid jets. In putting these suggestions into practice, abandoned U. S. application Ser. No. 563,234 discloses use of two spaced oppositely directed pneumatic false twisters operating on the runnng yarn.

It is an object of the present invention to provide a new process and apparatus for achieving levels of compaction with pneumatic false twisters higher than heretofore attainable.

Other objects and advantages of the invention will become apparent from the following detailed description in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic view of the apparatus in accordance with the invention;

FIG. 2 is a perspective view of the slub catcher or oscillating damping guide of FIG. 1;

FIG. 3 is a transverse vertical section through one of the jets of FIG. I;

FIG. 4 is an enlargement of a portion of FIG. 3; and

FIG. 5 is a perspective view of the jets and air supply of FIG. I.

In accordance with the invention, it has been found that the desired effect of higher compaction levels can be achieved if the two pneumatic false twisters are of different dimensions from one another. Specifically, if both are supplied with to same pressurized fluid, e.g. the same compressed air, it has been found advantageous to make the cross-sectional area of the yarn passage of the downstream twister smaller than that of the upstream twister. The yarn passages are generally circular in cross-section and the area of the upstream passage is about 150 to 300 percent that of the downstream passage and preferably about 200 to 250 percent.

The particular apparatus sets up complex forms of wave motions in the running yarn between the oppositely acting false twisters as well as upstream and downstream thereof and in accordance with a further aspect of the invention a damping guide is included to limit oscillation in the running end of yarn upstream of the apparatus, further increasing the compaction level.

Referring now more particularly to the drawings, in FIG. 1 there is shown a multifilarnent yarn 12 running from a source (not shown) which may be an extrusion cabinet or a package, the yarn making a 20 wrap, as indicated, around a circular pin 14, then passing through the slot of a damping guide 16 described more fully hereinafter. The yarn next passes through a passage in upstream pneumatic false twister 18, thence through a passage in downstream pneumatic false twister 20. In this embodiment twisters 18 and 20 are integral and share a common base 22 through which air is supplied as shown more clearly in FIGS. 3 and 5. The yarn 12 after leaving the downstream twister 20 passes to a guide 24 which is the balloon guide of a conventional ring and traveller takeup for collecting yarn on a bobbin 26 carried on a rotating spindle 28.

The damping guide 16 is of the type conventionally known as a slub-catcher." It comprises a flat plate 30 carrying a pair of wear-resistant inserts 32,34 defining therebetween a narrow slot of precise dimension. In the event of an enlargement in the yarn,.i.e. a slub, it will be caught by the inserts 32,34 and prevented from advancing. In the instant apparatus the guide 16 serves to confine the oscillations created in the yarn to the pneumatic false twisting zone thereby intensifying the compaction action.

In FIG. 3 there is shown a section through the upstream false twister 18, approximately to scale. In the block of metal making up twister 18 there is a notch 36 communicating with a slot 38 through which a yarn may be introduced or strung up into yarn passage 40. The yarn passage 40 runs the length of twister l8 and approximately halfway along its length it is intersected near its top by an air passageway 42 preferably of circular cross-section for ease of formation. Passageway 42 communicates with a further passageway 44 in base 22 through which compressed air is supplied by a coupling 46 (FIG. 5) to both twisters I8 and 20.

As can be seen in FIG. 4, the air passageway 42 is essentially tangential to the yarn passage 40 so that compressed air leaving passageway 42 will swirl around the periphery of passage 40 and create a vortex. Filaments of the yarn 12 caught .in the swirling air stream will tend to be tisted and the non-uniform action across the filament bundle will result in the desired compaction, in cooperation with the other twister 20, i.e. by itself twister 18 would put false twist into the yarn. By false twist is meant temporary twist; thus the yarn has twist while it is under the influence of the twister but some distance downstream of the nozzle this twist will have been lost and the yarn restored to its initial twist level, in this case zero twist.

The compressed air passageway 42 is preferably canted or tilted slightly off tangential to provide a more smoothly swirling stream and also to provide an air block which prevents accidentally blowing the yarn l2 out string up slot 38.

The twister is generally identical in structure with twister 18 with the exceptions that the swirling air stream is of oppsite sense and the yarn passage 48 is smaller in cross-sectional area than passage 40. Thus, whereas air passageway 42 enters from the right in FIG. 4 to create acounter-clockise vortex in twister 18, in twister 20 the air passageway entry to the bore would be at the left to create a clockwise vortex.

Somewhere between the twisters l8 and 2.0 the yarn 12 is under the influence of twisting forces from both twisters. Without wishing to be found thereby it is believed a helical wave configuration is imparted to the yarn in the upstream twister, the diameter of the helix being the diameter of the yarn passageway. A similar effect is produced in the second yarn passageway, ex-

' cept that the helix is now smaller in diameter. This greater intensity affects the location of the zone of twist reversal which is at some point between the two twisters, the decrease in the downstream diameter tending to move such point upstream. The complex wave motions, which are mechanical in character, interact and cause the filaments in the yarn individually or as subbundles to be displaced relative to neighboring filaments and sub-bundles to effect the compaction. This is to be distinguished from a false twisting of the entire bundle where there would be no interlacing and compaction.

Regardless of the theory, however, higher levels of compaction have been achieved using the instant system. Yarns upon which the invention can operate include all .multifilarnent yarns of polymers such as cellulosics, e.g. cellulose acetate and triacetate and rayon, nylons such as polyhexamethylene adipamide, polycaprolactam and polymers of other dicarboxylic acids and diamines or aminocarboxylic acids, polyesters such as polyethylene terephthalate and polymers of one or more other dicarboxylic acids and glycols, vinylidene polymers such as olefins, e.g. polyethylene and polypropylene, vinyl chloride and/or vinylidene chloride, acrylonitrile, and the like. Even silk or glass or metal filament yarns may be so processed. in addition, filaments of different chemical composition can be worked upon simultaneously and they will be interlaced and effectively blended at the same time. If desired, staple fiber yarn may be processed simultaneously with a continuous filament yarn and some of the staple fibers will be locked in the final structure.

The denier of the individual filaments may be as high as 50 or more or as low as 0.5 denier or less. The tension on the yarn in grams per denier may have to be lowered and the air pressure may have to be adjusted upwardly to permit interlacing of heavy denier filaments and opposite adjustment should be made of very low denier filaments. The pressure of the air used may range from as low as about 20 psig up to about l00'or more but for ease of achievement with inexpensive equipment, for safety and practicality the pressure desirably ranges from about 40 to 80 and preferably about 60 to psig.

The pressure in each twister may be different but is preferably the same, using a single common supply. The preferred pressurized fluid is air but steam, nitrogen, carbon dioxide, and the like, may be used. The temperature is dependent solely on the physical properties of the yarn and convenience, with ambient temperature therefore being preferred.

The tension on the running yarn, measured upstrean of the jets, may be as low as 0.005 gram per denier and may be so high as to approach the breaking point of the filaments. Higher tensions, however, increase the change of breaking filaments which are weaker than normal, and they make it necessary to increase the air pressure to obtain a given degree of interlacing and compaction. Consequently, the tension is desirably kept below about 0.5 gram per denier and usually below about 0.1 gram per denier. it should be at least about 0.1 gram per denier and usually at least about 0.02 gram per denier to prevent the yarn from bulking under the influence of the air, i.e. forming loops, or being blwn out the string up slot. The tension may be adjusted by controlling the weight of the traveler when using a ring and traveler takeup.

The total denier of the yarn being subjected to the dual opposed false twisting may be several thousand denier, e.g. 4,000 or more, although generally it is below 1,500 and desirably it ranges from about 20 to 200 preferably about 40 to 1 50. For best results there :shgulglbe at least about 5 filaments, desirably at least about 8 and preferably at least about 10. The yarn being tested is generally without twist initially, although it may be collected with twist superimposed if desired, or it may be separately aftertwisted. The handling characteristics, however, will be equivalent to a yarn having a much higher level of real twist. Alternatively, the yarn may be collected without twist. Possibly the starting yarn may have some twist, e.g. 0.1 turn per inch or possibly as much as 1 turn per inch of even more. Should the yarn have such twist preferably the vortex of the first pneumatic false twister will be of opposite sense so as to open the yarn, i.e. if the yarn has a clockwise twist the first twister of the pair should have its air passageway so directed as to create a counterclockwise vortex. Otherwise, it is without moment which twister is first encountered.

The length of the yarn passage through each of the pneumatic twisting jets may range from about 0.3 to 4.00 inches, preferably from about 0.5 to 1.00 inches. To some extent the length is determined by the speed at which it is intended to run the system i.e. the length should be so chosen that the yarn will be subjected to the action of each vortex for about 0.0003 to 0.2 and preferably about 0.0005 to 0.003 seconds. Shorter times will result in the yarn not having been exposed to the action long enough to achieve the desired result, although this could be compensated to some extent by increasing the pressure. Longer exposure times are without detriment but increase the cost of the apparatus and require more room to accommodate the lengthened structure.

The spacing between the two twisters may also be varied and generally ranges from about 0.l to 24 and preferably 0.5 to 1.5 inches. Outside of these ranges it is found that the degree of comaction tends to diminish somewhat. The cross-sectional area of each bore may vary within relatively wide limits and will, of course, be

- large enough to permit a vortex to be created and to accommodate the running yarn as well. When operating with textile deniers, e.g. 150 denier or less, the crosssectional area occupied by the yarn is so small that it can be ignored. The cross-sectional area of the smaller downstream bore may range from about 0.001 to 0.015 and preferably 0.002 to 0.01 sq. in. The upstream bore will have an area ranging from about 150 to 300 percent that of the downstream bore and preferably about 200 to 250 percent. lit has been found that operating within these ranges tends to produce the highest degree of compaction'in a given system, in contrast with using either bores of equal cross-sectional area or positioning the bore of larger cross-sectional area downstream.

The air passageway may be slighity off tanger tial as shown in FIG. 4 or it may be perfectly tangential i.e. the uppermost portion of the passageway being tangential to the circumference of the circular yarn passage. If the axis or the lower edge of the air passageway is tangential to the yarn passage, some measure or turbulence will result because the air will not be smoothly deflected into a rotating stream or vortex. hile the air passageway is shown in FIG. 4 as adjacent the yarn string up slot, it could of course be displaced 90 or more degress about the circumference of the yarn passage or, it is even possible to operate without a string up slot, in

.which case it will be necessary to thread the yarn through the passage with a needle each time there is a yarn discontinuity. The size and the cross-sectional area of the air passageway should be as small as practical to minimize the consumption of pressurized fluid;

. in practice, diameterranges from about 0.010 to 0.050

inches and preferably 0.018 to 0.024- inches have been found suitable for both the upstream and downstream twisters. As seen in plan, the air passageway will intercept the yarn passage approximately midway along the latters length and the air passageway may be perpendicular to the yarn passage or it may be directed at any angle relative thereto, decreasing the tension on the yarn if forwardly directed and increasing the yarn tension if .rearwardly directed. The air passageway may define an angle of about 75 to about 85 and preferably about 80 with the yarn pasage and directs air forwardly.

The slub catcher or damping guide shown in P16. 2 will have a slot whose dimension is dependent upon the diameter of the yarn bundle i.e. its denier. The width of the slot should be about 40 to 150 percent and preferably 50 to 100 percent the diameter of the bundle to be effective. With 55 and 75 denier yarns a slot width of about 0.003 0.008 inch and especially 0.004 inch has been found quite satisfactory. In addition to catching enlargements in the yarn, the guide serves to dampen oscillation in the yarn being subjected to the pneumatic false twisting action. For maximum effect i.e. the highest degree of compaction, it has been found that the guide should be positioned about 0.1 to 1.5 and preferably 0.25 to 1 inch upstream of the upstream jet. While a similar guide may be positioned downstream of the dwonstream jet it does not have the same effect on increasing compaction relative to the general system without such guides. The slub catcher eliminates the formation of small loops which otherwise are sometimes found on the first portion of yarn wound on a new bobbin. Its presence also permits use of a lower weight traveler and thus of less tension on the yarn, with attendant increase in compaction. The damping function may be performed with a flat guide over which the yarn runs and makes a sharp angle, thereby limiting oscillation. One may position a further guide downstream of the downstream jet properly to define the yarn path through the jets. The downstream guide may be of similar form and its location is not critical. Desirably, however, this downstream guide may be the balloon guide of a conventional ring and traveler takeup, which guide is about 0.375 to 1.5 and preferably 0.62 to 1.00 inch downstream of the downstream jet.

Reference has been made heretofore to the degree of compaction which refers to the extent of interlacing between the filaments. in a twisted yarn, the greater the twist the more compact will be the bundle, i.e. all filaments will be held tigtly together and none will stray from the bundle. lin interlaced yarn such as produced in accordance with the present invention which yarns generally have no twist, the degree of comaction is determined as follows:

A pin is put through a yarn sample (pretensioned to a value equal to 0.2 times the denier of the yarn expressed in grams) and is pulled longitudinally through the yarn until, as a. result of encountering interlacings and cross-overs amongst filaments, the incremental force required. toadvance the pin further exceeds denier per filament as grams tension. The-distance in centimeters which the pin has moved is measured and the average of 20 such measurements is used as an index of the degree of compaction. (llt will then be understood that lower needle pull values represent the higher levels of compaction.) Since the compaction may vary from inside to outside of each bobbin, the measurements should take this into consideration and should include beginning, middle and end run samples. The measurement of compaction may also be accomplished semi-automatically in accordance with the teachings of copending and commonly assigned application Ser. No. 812,219 filed April 1, 1969, by Bulla et al., now U.S. Pat. No. 3,566,683.

The invention will be further described ing illustrative examples.

EXAMPLE 1 A zero twist cellulose acetate yarn made up of 15 filaments and having a total denier of 55 is processed through the apparatus of F116. 1 at a speed of about 900 meters per minute. in this run the yarn makes a 0.wrap in contact with pin M which has a diameter of 0.16 inch and the center line of which is 0.455 inch upstream of twister 18. The yarn passes freely through the 0.004 inch wide slot of oscillation damping guide 16 provided 0.375 inches upstream of jet l8. Jets 18 and 20 are each 0.56 inch long and are spaced apart 0.5 inch. The cross-sectional area of the yarn passage of jet 18 is 0.007 sq. in. and that ofjet 20 is 0.003 sq. in., both yarn passages being circular in shape. The air passageway to each yarn passage is circular'in shape and has a diameter of 0.021 inch. As viewed from above, air enters each yarn passage at an angle, canted forwardly, at a location mid-way along its length. The pressurized fluid is at a pressure of 60 psig and is discharged at the rate of about 0.5 scfm per jet. The yarn string up slots 38 have a width of 0.005 inch. Threein the followfourths inch downstream of downstream jet 20 the yarn encounters balloon guide 24 from whence it is collected in conventional manner, by ring and traveller takeup, on a bobbin 26 rotating at a speed of 6,500 rpm witha traveler weighing 0.040 gm. The tension on the running yarn at a oint just upstream of pin 14 is measured at 2.5 grams. The degree of compaction of yarn on the bobbin is measured by first discarding several yards of yarn, followed by removal of a sample, backtwisting to remove all the twist imposed by the takeup,

i.e. restoring it to zero twist condition, nd carrying out the measurements as described hereinabove. The degree of compaction averaged 2.5 cms. as measured by the needle pull test.

EXAMPLE 2 In a manner similar to that described in Example 1,

' but employing no oscillatory damping guide a series of Ratio of upstream to downstream Threadline Compaction, bore diameter Tension, gms. cms. inches EXAMPLE 3 The run of Example 1 was repeated, utilizing a traveler weight of 0.065 grams. Threadline tension averaged about 3 .2 grams, and compaction values averaged 2.9 cm. over 24 bobbins, with individual values ranging between 1.8 and 3.8 cm. In an otherwise identical run without the oscillatory damping guide, threadline tension averaged about 3.6 grams, and compaction values averaged 5.0 cms. over 12 bobbins.

EXAMPLE 4 The process of Example 1 is repeated with the following changes: The yarn is 75/20 zero twist cellulose acetate. The spacing between jets l8 and 20 is 1 inch. The average yarn tension is about 3 grams. In this run, the pin 14 is positioned so the yarn makes a 20 wrap around it before passing through the damping guide and entering the yarn passages axially. The air pressure is 70 psig. The traveler weight is 0.065 gram. The average compaction is 2.5 cm.

EXAMPLE A 55/15 zero twist cellulose triacetate yarn and a 20/7 zero twist nylon 66 yarn are passed simultaneously through an apparatus as used in Example 1 with the following changes:

The speed is 750 meters per minute. The jets are spaced apart 0.5 inch. The traveler weight is 0.032 gram and the tension on the yarn averages 3.0 grams. The compactness of the well plied yarn is about 2.5 cm.

In the foregoing examples the desired result is achieved with little or no reduction in the physical properties of the yarn. Similarly, the jets undergo little if any wear although preferably the yarn passages are provided in removable, replaceable inserts made of special wear resistant materials.

The yarn is preferably subjected to the instant treatment after extrusion and prior to its initial collection although it may have been collected and subjected to the treatment in the course of twisting, plying, drawwinding, draw-twisting, beaming, or even weaving or knitting.

Various changes and modifications may be made without departing from the spirit and scope of the present invention and it is intended that such obvious changes and modifications be embraced by the following claims.

What is claimed is:

1. In an apparatus for the interlocking of a multifilament yarn comprising a pair of spaced members provided with aligned yarn passages which are circular in cross-section, each member being further provided with a fluid passageway generally tangential to its respective yarn passage, the senses of said two fluid passageways being opposite one another, means for advancing a multifilament yarn through said members, and means for introducing fluid to each of said passageways thereby to create a clockwise flow of fluid in one member and a counterclockwise flow of fluid in the other so as to tend to false twist the yarn in opposite directions in each member, with overall effect of interlacing said filaments, the improvement which comprises providing one member of said pair with a yarn passage which is from to 300 percent larger in crosssectional area than the other of said members.

2. The apparatus of claim 1, wherein the upstream member of said pair is provided with a yam passage larger in cross-sectional area than the downstream member yarn passage.

3. An apparatus according to claim 1 wherein said members range in length from about 0.3 to 4.00 inches and wherein the spacing between said members ranges from about 0.1 to 24 inches.

4. An apparatus according to claim 3, wherein said members are each provided with a slot running the length thereof and communicating throughout its length with the respective yarn passage, whereby yam may be introduced through said slots, said fluid passageways communicating with their respective yarn passages adjacent the respective slots, thereby shielding said slots and preventing yarn from accidentally being blown out said slots.

5. An apparatus according to claim 1, including a damping guide positioned from about 0.1 to 1.5 inches upstream of said upstream member to dampen upstream wave motion in yarn running through said members.

6. An apparatus according to claim 1, including a ring and traveller takeup having a balloon guide thereabouts, said balloon guide being located about 0.375 to 1.5 inch downstream of said downstream member.

7. An apparatus according to claim 1, including a guide positioned upstream of said upstream member to ensure the yarn would move through said members substantially axially in the absence of fluid introduced through said passageways.

8. An apparatus according to claim 7, wherein said guide is a substantially circular pin about which said yarn makes a partial wrap, said apparatus also including a damping guide positioned between said pin and the upstrearnmember. to dampen upstream wave motion in yarnrunning through said members.

9. The process for interlacing the filaments of a multifilament yarn to impart thereto the characteristics of a twisted yarn, which comprises passing said yarn consecutively through a pair of spaced zones, establishing in each zone a vortical flow of fluid whose rotational axis coincides substantially with the yarn pathwhen said fluid is inactive, the vortices being opposite in sense from one another, the cross-sectional area of one of said zones being larger than that of the other of said zones and collecting the yarn after passage through said downstream zone.

10. The process of claim 9, wherein the crosssectional area of the downstream zone is larger than that of the upstream zone.

11. The process of claim 10, wherein the collected yarn exhibits a needle pull value of below 2.5 cms 12. The process of claim 9, wherein the yarn, under the influence of the torqueing forces applied by the fluid vortices of the respective zones, assumes-as a bundle a rotating configuration characterized by a nodal pattern of helical wave form.

13. The process of claim 12 wherein filaments and groups of filaments within the yarn are wrapped about the yarn bundle and each other by the torqueing forces applied by the vortices of the respective zones.

14. The process of claim 13 wherein yarn bundle rotation is confined to form a short wave length nodal pattern of helical wave form between the point of con finement and the entrance to the first treatment zone.

15. The process of claim 9 wherein the vortices form in each treatment zone a spiral flow pattern along the direction of yarn travel, whereby the yarn is subjected to relatively continuous torqueing forces during its traverse of said zone.

16. The process of claim 9, wherein the torqueing forces applied to the yarn by the fluid vortices of the respective zones are balanced to provide a point of twist reversal between the said zones.

17. The process of claim 9, wherein the torqueing forces applied to the yarn by the fluid vortices of the respective zones are balanced to provide a point of twist reversal toward the end of the first treatment zone.

18. A process for the production of an interlaced multifilament 55 denier cellulose acetate yarn comprising passing said yam under a tension of less than about 0.5 grams per denier through a pair of oppositely acting confined fluid vortices in series, the confined vortices being of different cross-sectional areas and collecting a yarn characterized by a needle pull value of between about 2.5 and 2.7 cms.

19. The process of claim 18, wherein said fluid is applied to said yarn at the same pressure and velocity in each of said vortices. 

1. In an apparatus for the interlocking of a multifilament yarn comprising a pair of spaced members provided with aligned yarn passages which are circular in cross-section, each member being further provided with a fluid passageway generally tangential to its respective yarn passage, the senses of said two fluid passageways being opposite one another, means for advancing a multifilament yarn through said members, and means for introducing fluid to each of said passageways thereby to create a clockwise flow of fluid in one member and a counterclockwise flow of fluid in the other so as to tend to false twist the yarn in opposite directions in each member, with overall effect of interlacing said filaments, the improvement which comprises providing one member of said pair with a yarn passage which is from 150 to 300 percent larger in cross-sectional area than the other of said members.
 2. The apparatus of claim 1, wherein the upstream member of said pair is provided with a yarn passage larger in cross-sectional area than the downstream member yarn passage.
 3. An apparatus according to claim 1 wherein said members range in length from about 0.3 to 4.00 inches and wherein the spacing between said members ranges from about 0.1 to 24 inches.
 4. An apparatus according to claim 3, wherein said members are each provided with a slot running the length thereof and communicating throughout its length with the respective yarn passage, whereby yarn may be introduced through saiD slots, said fluid passageways communicating with their respective yarn passages adjacent the respective slots, thereby shielding said slots and preventing yarn from accidentally being blown out said slots.
 5. An apparatus according to claim 1, including a damping guide positioned from about 0.1 to 1.5 inches upstream of said upstream member to dampen upstream wave motion in yarn running through said members.
 6. An apparatus according to claim 1, including a ring and traveller takeup having a balloon guide thereabouts, said balloon guide being located about 0.375 to 1.5 inch downstream of said downstream member.
 7. An apparatus according to claim 1, including a guide positioned upstream of said upstream member to ensure the yarn would move through said members substantially axially in the absence of fluid introduced through said passageways.
 8. An apparatus according to claim 7, wherein said guide is a substantially circular pin about which said yarn makes a partial wrap, said apparatus also including a damping guide positioned between said pin and the upstream member to dampen upstream wave motion in yarn running through said members.
 9. The process for interlacing the filaments of a multifilament yarn to impart thereto the characteristics of a twisted yarn, which comprises passing said yarn consecutively through a pair of spaced zones, establishing in each zone a vortical flow of fluid whose rotational axis coincides substantially with the yarn path when said fluid is inactive, the vortices being opposite in sense from one another, the cross-sectional area of one of said zones being larger than that of the other of said zones and collecting the yarn after passage through said downstream zone.
 10. The process of claim 9, wherein the cross-sectional area of the downstream zone is larger than that of the upstream zone.
 11. The process of claim 10, wherein the collected yarn exhibits a needle pull value of below 2.5 cms.
 12. The process of claim 9, wherein the yarn, under the influence of the torqueing forces applied by the fluid vortices of the respective zones, assumes as a bundle a rotating configuration characterized by a nodal pattern of helical wave form.
 13. The process of claim 12 wherein filaments and groups of filaments within the yarn are wrapped about the yarn bundle and each other by the torqueing forces applied by the vortices of the respective zones.
 14. The process of claim 13 wherein yarn bundle rotation is confined to form a short wave length nodal pattern of helical wave form between the point of confinement and the entrance to the first treatment zone.
 15. The process of claim 9 wherein the vortices form in each treatment zone a spiral flow pattern along the direction of yarn travel, whereby the yarn is subjected to relatively continuous torqueing forces during its traverse of said zone.
 16. The process of claim 9, wherein the torqueing forces applied to the yarn by the fluid vortices of the respective zones are balanced to provide a point of twist reversal between the said zones.
 17. The process of claim 9, wherein the torqueing forces applied to the yarn by the fluid vortices of the respective zones are balanced to provide a point of twist reversal toward the end of the first treatment zone.
 18. A process for the production of an interlaced multifilament 55 denier cellulose acetate yarn comprising passing said yarn under a tension of less than about 0.5 grams per denier through a pair of oppositely acting confined fluid vortices in series, the confined vortices being of different cross-sectional areas and collecting a yarn characterized by a needle pull value of between about 2.5 and 2.7 cms.
 19. The process of claim 18, wherein said fluid is applied to said yarn at the same pressure and velocity in each of said vortices. 